1. Field of the Invention
The disclosed concept relates generally to machinery and, more particularly, to can decorator machines for decorating cans used in the food and beverage packaging industries. The disclosed concept also relates to ink station assemblies for can decorator machines.
2. Background Information
High speed continuous motion machines for decorating cans, commonly referred to as can decorator machines or simply can decorators, are generally well known. A typical can decorator is disclosed in commonly assigned U.S. Pat. No. 5,337,659. The can decorator includes an in-feed conveyor, which receives cans from a can supply (not shown) and directs them to arcuate cradles or pockets along the periphery of spaced parallel rings secured to a pocket wheel. The pocket wheel is fixedly secured to a continuously rotating mandrel carrier wheel or turret. The turret, in turn, is keyed to a continuously rotating horizontal drive shaft. Radial/horizontal spindles or mandrels, each being rotatable about its own axis, are mounted to the mandrel carrier wheel adjacent its periphery. Downstream from the in-feed conveyor, each mandrel is in closely spaced axial alignment with an individual pocket and undecorated cans are transferred from the pockets to the mandrels. Suction applied through an axial passage of the mandrel draws the can to a final seated position on the mandrel.
While mounted on, and rotating with, the mandrels, the cans are decorated by being brought into engagement with a blanket (e.g., without limitation, a replaceable adhesive-backed piece of rubber) that is adhered to a blanket segment of a multicolor printing unit. Thereafter, and while still mounted on the mandrels, the outside of each decorated can is coated with a protective film of varnish applied by engagement with the periphery of an application roll in an over-varnish unit. Cans with decorations and protective coatings thereon are then transferred from the can decorator for further processing.
Application of ink to the can is accomplished as follows. Prior to engagement with an undecorated can, the blanket engages a plurality of printing cylinders, each of which is associated with an individual ink station assembly. That is, each ink station is one of a plurality of printing stations. An ink station assembly includes an ink fountain and a plurality of rolls, typically about ten rolls. The next to final roll is a printing cylinder. The printing cylinder applies the ink to the blanket which, in turn, applies the ink to a can. Each ink station assembly provides a different color ink and each printing cylinder applies a different image segment to the blanket. All of these image segments combine to produce the main image. This main image is then transferred to undecorated cans.
This configuration has several disadvantages. For example, to maintain the mandrels spinning at a speed corresponding to the speed of ink stations, a complex system of gears, and other motion transmission elements, couples the mandrels to the turret and ink stations. Each element of such a system is subject to wear and tear. Further, all linked elements of the system rotate at the same time. Thus, for example, the various rolls of the print stations rotate when the turret rotates, even if no cans are being decorated, e.g. during initialization of the system.
Further, in this configuration, the horizontally extending drive shaft of the turret is subjected to a moment arm due to the weight of the turret and mandrels. This moment arm is not desirable as the force causes additional wear and tear. Also, the linked elements of the drive assemblies cause unneeded wear and tear on elements that are not in use at the same time. Additionally, the mechanical elements required for linked drive assemblies have a weight that must be supported. Thus, the decorator assembly housing assembly must be more robust. This is in contrast to other configurations, such as, but not limited to, a cantilever configuration for an ink station which is less massive than known designs. Further, the printing cylinder includes a fixed print image. As such, changing the image requires changing the printing cylinder, which is a time consuming process. As such, printed indicia, such as a sequential serial number cannot be printed by the printing cylinder. Also, print cylinders are typically disposed below the mandrel upon which a can being decorated is disposed. In this configuration, excess ink may be sprayed upward and outward in a broad pattern. There is, therefore, room for improvement in can decorating machines and ink station assemblies.